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Lee H.L.,KAIST | Moon S.-M.,RF and Satellite Payload Research Team | Yu J.-W.,KAIST
Microwave and Optical Technology Letters | Year: 2014

This article presents a K-band reconfigurable 4 × 4 balanced high power amplifier (HPA) adopting voltage-controlled phase inverters which can precisely provide relative phase shifts of 0 and 180. By properly adjusting the relative phases in the 4 × 4 array paths of the proposed structure, a fixed input-to-output port relationship of the conventional balanced PA can be overcome through the improvement in output flexibility. The proposed 4 × 4 balanced HPA is configured by four K-band HPA microwave monolithic integrated circuits (MMICs), four phase inverter MMICs, and two 4 × 4 waveguide-Butler matrices as input and output passive networks. Each K-band HPA is fabricated with 0.15-μm pHEMT process and has the size of 4.26 × 2.35 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2820-2822, 2014 Copyright © 2014 Wiley Periodicals, Inc.


Lee H.L.,KAIST | Moon S.-M.,RF and Satellite Payload Research Team | Yu J.-W.,KAIST
Microwave and Optical Technology Letters | Year: 2014

Two types of compact broadband phase shifter MMICs (monolithic microwave integrated circuits) with constant insertion loss variations are presented. Both phase shifters are reflection-type phase shifters using a Lange coupler as a 3-dB coupler and LC resonance terminations. The first type phase shifter uses a single diode with reverse biasing as a varactor and adopts a miniaturized Lange coupler to maximize compactness and to minimize parasitic loss. The second type adopts back-to-back connected diodes with reverse biasing as a varactor for wider tunable phase range and parallel resistors for constant insertion loss variation. For both types, MMIC's are fabricated in GaAs 0.15-μm low noise pHEMT (p-high electron mobility transition) process and required indcutances are implemented by microstrip lines. The implemented MMIC phase shifter of the first type shows the measured relative phase shift range of 80 and measured insertion loss of 2.1 ± 0.2 dB at 20 GHz. The measured relative phase shift range of 72 ± 9 and the measured insertion loss variation of ±0.2 dB are obtained from 15 to 25 GHz. Similarly, the second type phase shifter shows the measured relative phase shift range of 104 and measured insertion loss of 2.4 ± 0.1 dB at 21 GHz. Also, the broadband characteristic of the second type is verified by the measured relative phase shift range of 96 ± 8 with the constant insertion loss variation of ±0.2 dB from 17 to 25 GHz. © 2014 Wiley Periodicals, Inc.


Lee H.L.,KAIST | Moon S.-M.,RF and Satellite Payload Research Team | Dong H.-J.,University of Seoul | Lee M.-Q.,University of Seoul | Yu J.-W.,KAIST
Electronics Letters | Year: 2013

K-band 0°/180° phase shifter MMIC based on balanced structure which can be applied to BPSK or QPSK modulator with dc-offset cancellation is presented. The proposed balanced phase shifter consists of four Lange couplers, two quarter-wave transmission lines and four switches for open and short terminations. The proposed structure implemented in GaAs 0.15-μm low noise pHEMT process ensures stable 0/180° phase shift while common-mode signals due to the mismatch in reflections by open and short are fed to the isolation port. The proposed phase shifter is verified by the phase shift of 179 ± 1.5° with the insertion loss of 4.5 ± 0.8 dB from 17.5 to 22.5 GHz. The fabricated phase shifter size is 2.2 × 2.85 mm including test pads. © The Institution of Engineering and Technology 2013.


Lee H.L.,KAIST | Moon S.-M.,RF and Satellite Payload Research Team | Lee M.-Q.,University of Seoul | Yu J.W.,KAIST
Electronics Letters | Year: 2014

A wideband six-port-based demodulator is proposed and applied as a quadrature phase shift keying (QPSK) demodulator for optimal K-band multiport amplifier (MPA) calibration circuitry. The proposed six-port demodulator adopts wideband ring hybrids for optimal 180° phase balance in local oscillator signal paths. In addition, a voltagecontrolled reflection-type phase shifter and an attenuator are integrated into the six-port structure to ensure accurate magnitude and phase balance over broadband operation, resulting in optimal phase and amplitude error detection for the MPA system. To verify the proposed structure, RF demodulation of the K-band QPSK modulated signal was demonstrated for purpose of MPA calibration. © The Institution of Engineering and Technology 2014.


Lee H.-L.,KAIST | Moon S.-M.,RF and Satellite Payload Research Team | Lee M.-Q.,University of Seoul | Yu J.-W.,KAIST
Journal of Electromagnetic Waves and Applications | Year: 2013

This letter presents a simple but efficient phase shift range enhancement technique for a reflection type phase shifter (RTPS). The proposed structure consists of a 3-dB coupler and a pair of back-to-back diodes connected with a pair of series and parallel inductors and a pair of parallel resistors. The parallel inductors are inserted to widen relative phase shift range compared to regularly used RTPS and Lange coupler is used as the 3-dB coupler. The proposed circuit is implemented in 0.15 -μm GaAs low noise pHEMT process and provides a measured phase shifting range of 227° at 24 GHz with a measured insertion loss of 4.6 ± 1.3 dB. The input and output return losses are better than 18 dB and 17 dB, respectively. The size of the fabricated phase shifter MMIC chip is 2.2×1.5 mm2 including test pads. © 2013 Copyright Taylor and Francis Group, LLC.


Jeong J.C.,RF and Satellite Payload Research Team | Yom I.B.,RF and Satellite Payload Research Team
Electronics Letters | Year: 2011

An X-band high power multi-function chip has been designed and fabricated using 0.25m SiGe BiCMOS technology, for a transmit/receive (T/R) module of phased array radar systems. The high power and wideband performance was achieved by the integrated power amplifiers employing an active bias circuit and a series feedback technique. The fabricated multi-function chip with a compact size of 8.4mm 2 (3.5×2.4mm) exhibits a transmit/receive gain of 30/20dB and a P1dB of 18dBm from 8 to 11GHz. © 2011 The Institution of Engineering and Technology.

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